After searching and readding on diferent questions about this topic. Still didn't find a solution.
I am working in a local server. In wampserver. My wordpress folders are inside a myfolder. Inside wp-content and in themes I have my theme template.
Looks like this:
In the other themes I am getting the same call. And itsn't just the function get_header. Other functions are also undefined. So, it seems the problem comes calling to wordpress functions.
Have reinstaled Wordpress and still having the same problemo.
I have all wordpress folders. I am sure it has to be something wrong from the themes to wordpress folders. But it looks everything fine.
In other way, from wampserver/localhost/mypage I can see the website. But, in my editor (phpstorm) i get all the functions with another color telling me that they are undefined. The browser links from editor brings me to this "Fatal call function undefined..."
I am using Underscore me template. Maybe am I doing something wrong with Underscore?
or maybe it´s just a settings problem with phpstorm? In this case would not be a Wordpress issue I guess...
Thanks for your help!